An image forming apparatus is an apparatus capable of forming text and images on a printing medium. For an image forming apparatus using a photo-imaging method, a processing cartridge is the most important component. A photosensitive component in the processing cartridge can convert image information into an electronic latent image, and then convert the electronic latent image into a solid toner image and transfer the toner image to the print medium. The processing cartridge contains toner, and as the printing operation continues, the toner is gradually consumed. Therefore, the processing cartridge is a consumable item and needs to be replaced frequently.
Currently, the common processing cartridges on the market include undetachable cartridges and detachable cartridges. Replacing an undetachable cartridge requires the user to re-purchase a processing cartridge or add toner to the processing cartridge. However, in practice, when the toner is consumed, the lifetime of the photosensitive component may still not be reached, so re-adding the toner may be the only thing needed in order to continue the use. However, for users, adding the toner may be very inconvenient, and may easily cause pollution. Therefore, with the current emphasis of environmental protection, using detachable cartridges becomes more favored.
Although the detachable type processing cartridge is more convenient to use, during the design process, the requirements on the matching accuracy between different parts may be higher. In particular, for a developing roller in the developing cartridge and a photosensitive drum in the photosensitive drum cartridge, if the clamping effect between the developing roller and the photosensitive drum is not sufficiently ensured, the printed image may have a significant quality problem. The conventional detachable type processing cartridges and image forming apparatuses are provided with a pushing component for respectively providing forces in two different directions to push the developing cartridge such that the developing roller can be maintained in contact with the photosensitive drum, and also press the processing cartridge such that the mounting of the processing cartridge in the image forming apparatus becomes more stable. According to the existing technology, in order to resist the rotational torque generated when the photosensitive drum rotates and the thrust force of the photosensitive drum against the developing roller and also prevent the developing cartridge from being retracted back in the mounting direction, the thrust force for pushing the developing cartridge is set to be relatively large. However, this may cause the processing cartridge to be partially subjected to a relatively large counterforce of the thrust force, and the resin frame of the processing cartridge may be deformed if there is no sufficient strength to support. In addition, if the thrust force is set to be too small, the clamping force between the developing roller and the photosensitive drum may be too small, which may affect the print quality and cause blurred images.